Method for forming compact from powder and mold apparatus for powder forming

Abstract

A method for forming a compact from a powder wherein a forming portion 1 A in a mold body 2 is filled with a raw powder and upper and lower punches 3,4 are fitted into the forming portion 1 A to form the compact. Prior to filling the forming portion 1 A with the raw powder M, a solution L with a lubricant being uniformly dissolved in a solvent is applied to a peripheral portion of the forming portion 1 A, and then the solution is evaporated, thus forming a crystallized layer B thereon. Thus, the reduction of a force for ejecting the compact is realized, while improving the density of the compact, realizing the stable and successive production of the compact

1 . A method for forming a compact from a powder, comprising the steps of: 
 applying a solution obtained by dissolving a lubricant in a solvent to a forming portion of a mold body;    evaporating the solution to form a crystallized layer on a surface of the forming portion; filling the forming portion of the mold body with a raw powders; and fitting upper and lower punches into the forming portion.    
   
   
       2 . The method for forming a compact from a powder according to  claim 1 , wherein the lubricant comprises an oxo-acid-based metal salt.  
   
   
       3 . The method for forming a compact from a powder according to  claim 1 , wherein the lubricant is at least one selected from a group consisting of a phosphate metal salt, a sulfate metal salt, a borate metal salt, a silicate metal salt, a tungstate metal salt, an organic-acid-based metal salt, a nitrate metal salt and a carbonate metal salt.  
   
   
       4 . The method for forming a compact from a powder according to  claim 3 , wherein the lubricant is at least one selected from a group consisting of dipotassium hydrogen phosphate, disodium hydrogen phosphate, tripotassium phosphate, trisodium phosphate, potassium polyphosphate, sodium polyphosphate, riboflavin potassium phosphate and riboflavin sodium phosphate.  
   
   
       5 . The method for forming a compact from a powder according to  claim 3 , wherein the lubricant is at least one selected from a group consisting of potassium sulfate, sodium sulfate, potassium sulfite, sodium sulfite, potassium thiosulfate, sodium thiosulfate, potassium dodecyl sulfate, sodium dodecyl sulfate, potassium dodecylbenzensulfonate, sodium dodecylbenzenesulfonate, Food Blue No. 1., Food Yellow No. 5., potassium ascorbyl sulfate and sodium ascorbyl sulfate.  
   
   
       6 . The method for forming a compact from a powder according to  claim 3 , wherein the lubricant is potassium tetraborate or sodium tetraborate.  
   
   
       7 . The method for forming a compact from a powder according to  claim 3 , wherein the lubricant is potassium silicate or sodium silicate.  
   
   
       8 . The method for forming a compact from a powder according to  claim 3 , wherein the lubricant is potassium tungstate or sodium tungstate.  
   
   
       9 . The method for forming a compact from a powder according to  claim 3 , wherein the lubricant is at least one selected from a group consisting of potassium acetate, sodium acetate, potassium benzoate, sodium benzoate, potassium ascorbate, sodium ascorbate, potassium stearate and sodium stearate.  
   
   
       10 . The method for forming a compact from a powder according to  claim 3 , wherein the lubricant is potassium nitrate or sodium nitrate.  
   
   
       11 . The method for forming a compact from a powder according to  claim 3 , wherein the lubricant is at least one of potassium carbonate, sodium carbonate, potassium hydrogen carbonate and sodium hydrogen carbonate.  
   
   
       12 . (canceled)  
   
   
       13 . The method for forming a compact from a powder according to  claim 1 , wherein said solution has said lubricant completely dissolved in water to have a concentration greater than or equal to a concentration at which the thickness of a crystallized layer is formed by one molecule of the lubricant, but less than a concentration of a saturated solution.  
   
   
       14 . The method for forming a compact from a powder according to  claim 13 , wherein the lubricant is a potassium salt or a sodium salt.  
   
   
       15 . The method for forming a compact from a powder set forth in  claim 1 , wherein an antiseptic substance is added into the lubricant.  
   
   
       16 . The method for forming a compact from a powder set forth in  claim 1 , wherein a defoaming agent is added into the lubricant.  
   
   
       17 . The method for forming a compact from a powder set forth in  claim 1 , wherein soluble solvent is added into the lubricant.  
   
   
       18 . The method for forming a compact from a powder according to  claim 17 , wherein said solvent is alcohol or ketone.  
   
   
       19 . The method for forming a compact from a powder according to  claim 1 , wherein no halogen element is included in the lubricant.  
   
   
       20 . A mold apparatus for powder molding, comprising: 
 a mold body with a through-hole for forming a side of a compact;    a lower punch for fitting into the through-hole from beneath;    an upper punch for fittingh into the through-hole from above;    a spray pump for spraying a lubricant solution to the through-hole;    a heater provided around a forming portion of the mold body, the forming portion being defined by the through-hole and the lower punch; and    a temperature control system for keeping a temperature of the heater higher than an evaporating temperature of the solution.    
   
   
       21 . A mold apparatus for powder molding, comprising: 
 a mold body with a through-hole for forming a side of a compact;    a lower punch for fitting into the through-hole from beneath;    an upper punch for fitting into the through-hole from above;    a spray pump for spraying a lubricant solution to the through-hole;    a heater provided around a forming portion of the mold body, the forming portion being defined by the through-hole and the lower punch; and    a temperature control system for keeping a temperature of the heater higher than an evaporating temperature of the solution, but lower than a melting temperature of the lubricant.